900 research outputs found
Perché piacciono maghi e vampiri: letteratura, cognitivismo e controfattualità
Recenti test sul potenziale socio-cognitivo e il valore edonico di testi letterari che utilizzano elementi magici rivelano come la controfattualità costituisca una ‘palestra mentale’ per i lettori: essi apprendono a elaborare spiegazioni causali complesse e incrementano i fattori coinvolti nel costituirsi della coesione sociale, sia nel caso di lettori young adult sia nel caso di lettori adulti. Lo psicologo Eugene Subbotsky ha dimostrato che la magia ci rende più sensibili alle operazioni di Teoria della Mente e socialmente empatici, mentre un gruppo di narratologi ha di recente misu- rato i tempi di riassorbimento della dissonanza cognitiva prodotta dall’elemento magico: ciò rie- sce fra l’altro a spiegare il grande successo di Harry Potter e della saga di Twilight.L'articolo indaga i meccanismi contrattuali della letteratura dal punto di vista neurocognitivista
The immersive novel
The paper analyzes the emergence of an emotional immersion pattern in the works of authors of the contemporary bestselling such as Nobel prize winner Orhan Pamuk, in particular the novel The Museum of Innocence, the Hunger Games saga by Suzanne Collins and the Carlos Ruiz Zafón’s Tetralogy, El cementerio de los libros olvidados
Suspense is the Key. Narratology, Cognitive Neurosciences and Computer Technology
L'articolo indaga i meccanismi neurocognitivi alla base della suspense sia in ambito letterario che filmico
Symmetry decomposition of negativity of massless free fermions
We consider the problem of symmetry decomposition of the entanglement
negativity in free fermionic systems. Rather than performing the standard
partial transpose, we use the partial time-reversal transformation which
naturally encodes the fermionic statistics. The negativity admits a resolution
in terms of the charge imbalance between the two subsystems. We introduce a
normalised version of the imbalance resolved negativity which has the advantage
to be an entanglement proxy for each symmetry sector, but may diverge in the
limit of pure states for some sectors. Our main focus is then the resolution of
the negativity for a free Dirac field at finite temperature and size. We
consider both bipartite and tripartite geometries and exploit conformal field
theory to derive universal results for the charge imbalance resolved
negativity. To this end, we use a geometrical construction in terms of an
Aharonov-Bohm-like flux inserted in the Riemann surface defining the
entanglement. We interestingly find that the entanglement negativity is always
equally distributed among the different imbalance sectors at leading order. Our
analytical findings are tested against exact numerical calculations for free
fermions on a lattice.Comment: 48 pages, 7 figure
Entanglement resolution of free Dirac fermions on a torus
Whenever a system possesses a conserved charge, the density matrix splits
into eigenspaces associated to the each symmetry sector and we can access the
entanglement entropy in a given subspace, known as symmetry resolved
entanglement (SRE). Here, we first evaluate the SRE for massless Dirac fermions
in a system at finite temperature and size, i.e. on a torus. Then we add a
massive term to the Dirac action and we treat it as a perturbation of the
massless theory. The charge-dependent entropies turn out to be equally
distributed among all the symmetry sectors at leading order. However, we find
subleading corrections which depend both on the mass and on the boundary
conditions along the torus. We also study the resolution of the fermionic
negativity in terms of the charge imbalance between two subsystems. We show
that also for this quantity, the presence of the mass alters the equipartition
among the different imbalance sectors at subleading order.Comment: 45 pages, 8 Figure
Symmetry-resolved entanglement entropy in Wess-Zumino-Witten models
We consider the problem of the decomposition of the R\'enyi entanglement
entropies in theories with a non-abelian symmetry by doing a thorough analysis
of Wess-Zumino-Witten (WZW) models. We first consider as a case study
and then generalise to an arbitrary non-abelian Lie group. We find that at
leading order in the subsystem size the entanglement is equally distributed
among the different sectors labelled by the irreducible representation of the
associated algebra. We also identify the leading term that breaks this
equipartition: it does not depend on but only on the dimension of the
representation. Moreover, a contribution to the R\'enyi entropies
exhibits a universal form related to the underlying symmetry group of the
model, i.e. the dimension of the Lie group.Comment: 31 pages, v2: minor change
More on symmetry resolved operator entanglement
The `operator entanglement' of a quantum operator is a useful indicator
of its complexity, and, in one-dimension, of its approximability by matrix
product operators. Here we focus on spin chains with a global
conservation law, and on operators with a well-defined charge, for
which it is possible to resolve the operator entanglement of according to
the symmetry. We employ the notion of symmetry resolved operator
entanglement (SROE) introduced in [PRX Quantum 4, 010318 (2023)] and extend the
results of the latter paper in several directions. Using a combination of
conformal field theory and of exact analytical and numerical calculations in
critical free fermionic chains, we study the SROE of the thermal density matrix
and of charged local operators evolving in
Heisenberg picture . Our main results are: i) the
SROE of obeys the operator area law; ii) for free fermions, local
operators in Heisenberg picture can have a SROE that grows logarithmically in
time or saturates to a constant value; iii) there is equipartition of the
entanglement among all the charge sectors except for a pair of fermionic
creation and annihilation operators.Comment: 26 pages, 6 figure
Full counting statistics and symmetry resolved entanglement for free conformal theories with interface defects
We consider the ground state of two species of one-dimensional critical free
theories coupled together via a conformal interface. They have an internal
global symmetry and we investigate the quantum fluctuations of the
charge across the impurity, giving analytical predictions for the full counting
statistics, the charged moments of the reduced density matrix and the symmetry
resolved R\'enyi entropies. Our approach is based on the relation between the
geometry with the defect and the homogeneous one, and it provides a way to
characterise the spectral properties of the correlation functions restricted to
one of the two species. Our analytical predictions are tested numerically,
finding a perfect agreement
Entanglement asymmetry as a probe of symmetry breaking
Symmetry and symmetry breaking are two pillars of modern quantum physics.
Still, quantifying how much a symmetry is broken is an issue that has received
little attention. In extended quantum systems, this problem is intrinsically
bound to the subsystem of interest. Hence, in this work, we borrow methods from
the theory of entanglement in many-body quantum systems to introduce a
subsystem measure of symmetry breaking that we dub entanglement asymmetry. As a
prototypical illustration, we study the entanglement asymmetry in a quantum
quench of a spin chain in which an initially broken global symmetry is
restored dynamically. We adapt the quasiparticle picture for entanglement
evolution to the analytic determination of the entanglement asymmetry. We find,
expectedly, that larger is the subsystem, slower is the restoration, but also
the counterintuitive result that more the symmetry is initially broken, faster
it is restored, a sort of quantum Mpemba effect, a phenomenon that we show to
occur in a large variety of systems.Comment: 7 pages, 5 figures. Text reorganized, new results for interacting
integrable and non-integrable spin chains added. Final version published in
Nature Communication
Lack of symmetry restoration after a quantum quench: an entanglement asymmetry study
We consider the quantum quench in the XX spin chain starting from a tilted
N\'eel state which explicitly breaks the symmetry of the post-quench
Hamiltonian. Very surprisingly, the symmetry is not restored at large
time because of the activation of a non-abelian set of charges which all break
it. The breaking of the symmetry can be effectively and quantitatively
characterised by the recently introduced entanglement asymmetry. By a
combination of exact calculations and quasi-particle picture arguments, we are
able to exactly describe the behaviour of the asymmetry at any time after the
quench. Furthermore we show that the stationary behaviour is completely
captured by a non-abelian generalised Gibbs ensemble. While our computations
have been performed for a non-interacting spin chain, we expect similar results
to hold for the integrable interacting case as well because of the presence of
non-abelian charges also in that case.Comment: 25 pages, 5 figures. Typos corrected, references adde
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